Project Summary This project will study fifteen unilateral below-knee prosthesis users using six different prosthetic feet on five ramp surfaces (-10o, -5o, 0o, 5o, and 10o). Two of the six components are claimed to be adaptable to walking surface slopes. For each of these adaptable systems, two similar components will also be tested in an attempt to determine the effects of their approaches to adaptation on ramp walking. Each participant will use all components in a random order, making the study a randomized cross-over design. Measurements will focus on the effective torque experienced at the end of the residual limb socket, which should relate to pressures felt within the socket and required activation of muscles controlling the remaining knee. The torque versus angle characteristic at the ankle and the roll- over shape will also be measured to estimate the relative stiffness, the effective alignment (set-point) for each step, and the energy requirements of a system that would mimic the able-bodied system. Self-reported effort and comfort associated with the use of each prosthetic foot on the ramps will also be collected from prosthesis users in the study. Data will also be collected on age-matched able- bodied persons for comparison of their ankle-foot biomechanics on the various ramp surfaces with those of the prosthetic ankle-foot systems.